Internal combustion engine



April 26, 1932. E AHRENS 1,856,048

INTERNAL COMBUSTION ENGINE Filed Nov. 26, 1950 2 Sheets-Sheet l INVENTOR ATTORNEYS April 26, 1932.

E. C. AHRENS INTERNAL COMBUST ION ENGINE Filed Nov. 26, 1930 2 Sheets-Sheet 2 ATTORNEYS Patented Apr. 26, 1932 UNITED STATES ELMER G. AHRENS,

OF CLEVELAND, OHIO, ASSIGNOR OF ONE-HALF TO HENRY B.

AHRENS, F MONTCLAIR, NEW JERSEY INTERNAL COMBUSTION ENGINE Application filed November 26, 1930.

This invention relates to internal combustion engines and, among other objects, aims to provide an improved two-cycle engine of the general type disclosed and claimed in my copending application, Ser. No. 474,808, filed August 12, 1930. It contemplates an improved construction and mode of operation of a two-cycle engine wherein fuel mixture is initially compressed and discharged in into or admitted to a power cylinder by means of a reciprocating fuel pump associated with and driven by the engine. The main idea is to produce a relatively simple and very ef iicient engine capable of being driven at variable speeds and having a high volumetric efficiency.

Other important aims and advantages of the invention will appear in the specification, when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a vertical sectional view of an engine embodying the invention; and

Figs. 2 to 1 inclusive, are diagrammatic views showing the relative positions of the parts at different periods in the cycle of operations.

Referring particularly to the drawings, the invention is there embodied for the sake of simplicity in an engine (shown more or less diagrammatically) ,having only one power cylinder; although it is to be understood that it may have any desired number of cylinders. In this example, the engine has a crank case 10 and a cylinder block 11 bolted to the crank case. There are two adjacent cylinders 12 and 13 in the cylinder block, 12 being a power cylinder and 13 being a fuel pumping cylinder. A crank shaft 14 having a single crank 15 is shown as being arranged directly below the power cylinder 12 and a power piston 16 is connected to the crank by a connecting rod 17. A pumping piston 18 in the cylinder 13 is here shown as being connected to be driven by the connecting rod 17. In this instance, a connecting rod 19 for the pump piston is pivotally con nected at its lower end to an integral, laterally projecting arm 20 011 the connecting rod 17.

Referrin to Fi 1 the construction and a: g a

Serial N0. 498,465.

arrangement is such that the pumping iston reaches the outer or compression en of its stroke before the power piston reaches the outer end of its stroke. The lower end of the connecting rod 19 travels in an elliptical path as the crank rotates in a clockwise direction. The major axis of the path is at an acute angle to the axis of the Working piston.

In this example, the valves and valve passages are provided in a cover 21 for the cylinders. A fuel intake passage 22 communicates with the cylinder 13 and is controlled by an ordinary poppet valve 23. A fuel passage 24 is so arranged as to admit fuel to the power cylinder 12 from the pumping cylinder 18 and is controlled by a poppet valve 25. An exhaust passage 26 is controlled by another valve 27. It will be understood that all of the valves are adapted to be operated by ordinary cams (not shown), and they are opened and closed in proper sequence, hereinafter described. An ordinary spark plug 28 extends into the combustion chamber of the working cylinder to ignite the fuel charges therein.

In Fig. 1, all of the valves are shown as being closed. The power piston 16 is at the upper or outer end of its stroke; while the fuel pumping piston has started on its inward or suction stroke. hen the parts are in this position, the admitted fuel charge in the power cylinder has just been exploded and the piston 16 is about to start on its power stroke. The fuel admission valve 25 will remain closed until another fuel charge is ready to be admitted to the combustion chamber. The exhaust valve 27 is timed to remain closed until the piston 16 has traveled through the greater portion of its inward stroke. It is preferably opened before this piston reaches the end of its power stroke.

The fuel intake valve 23 for the pumping cylinder is timed to open after the pumping piston 18 starts on its inward or suction stroke. It is about to be opened when the parts are in the position shown in Fig. 1. That is the next event to take place in the cycle of operations. This valve will remain open until a fuel charge is admitted. It will then close and remain closed while the pumping piston compresses the charge and until after it starts on its succeeding inward or suction stroke.

Referring to the dotted paths of the crank pin 15, and the pivot pin connection between the connecting rod 19 and the arm 20, the

cycle of events can best be explained by corresponding points on the two paths. Beginning with the crank pin in its position as shown in Fig. 1, all of the valves will remain closed until it reaches a point between a and c on the crank circle or until the pivot pin on the connecting rod has traveled some distance toward the 0 on the ellipse. 1 The exact point'or position of the piston 18 when the intake valve 23 opens is determined by the pressure which exists in the clearance space of the pumping cylinder and the connecting fuel passage when it reaches the outer end of its stroke; The idea is to 'keep this valve closed until the pressure'in the pumping cylinder and the fuel passage is reduced slightly below atmospheric pressure caused by the inward movement of the pumping piston. The intake valve 23 will then remain open until the piston 18 reaches approximately the inner end or suction end of its stroke, or until the crank 15 has reached approximately the point it on the crank circle and the pivot pin has reached approximately the point h on the ellipse.

As hereinbefore stated, the fuel admission 'valve 25 will remain closed until a new charge is to be admitted to the power cylinder 12. It is timed to open slightly before the exhaust valve 27 opens so as to admit compressed fuel into the power cylinder and utilize it to assist in scavenging exhaust gases from the power cylinder. This valve 25 is preferably timed to open when the crank pin 15 is in the vicinity of the point m on the crank circle. The fuel charge in the pumping cylinder is then under high pressure and will immediately rush into the power cylinder. The charge of fuel must be admitted to the combustion chamber before the piston 16 reaches the outer end of its stroke so that it may be ignited shortly before the crank pin 15 reaches its outer dead center. In fact, the fuel admission valve 25 will close when the crank pin is in the vicin ity of the point p on the crank circle and before the ignition of the fuel charge takes place. It will thus be seen that the charge of fuel is admitted during only a small part of the exhaust stroke of the power piston,

' ivino' the aiston an o 3 ortunit to seaven 'e most of the exhaust gases from the power cylinder. The exhaust valve 27 opens before the power piston 16 reaches the inner end of "its expansion or power stroke. In this example, it is timed to open when thecrank pin 15' is in the vicinity of'the point 9 on the 'to come to rest.

crank circle and it will remain open until the crank pin has passed the point m or after the valve 25 opens and admits enough fresh fuel to assist in scavenging the remaining exhaust gases.

Referring now to the diagrammatic illustrations in Figs. 2, 3 and 4, it will be noted that the pistons 16 and 18 are shown in different positions. These views adequately disclose the cycle of operations'of the valves. In Fig. 2, the fuel intake valve23 is open and the fuel pumping piston is about halfway on its suction or inward stroke. Both the fuel admission valve- 25 and the exhaust valve 27 are closed while the power piston 16 is on its expansion or power stroke. In Fig. 3, the exhaust valve 27 has just opened and the valve 23 closed. Incidentally, the fuel pumping piston 18 has here reached the end of its inward or suction stroke, while the power piston 16 is still moving inwardly and will continue to move until the crank pin reaches the lower dead center as illustrated. In Fig-it, the fuel admission valve 25 for the power cylinder is opened; while the exhaust valve 27 is closed, it being understood that the valve 25 started to open just before the exhaust valve was closed. \Vhen the power piston is in this position, the pumping piston 18 has about reached the end of its compression stroke, so that the fuel charge is under very high pressure.

After the valve 25 opens, the fuel pumping piston gains rapidly on the power piston while the final compression pressure is being applied to the fuel mixture so as to cause the fuel to rush rapidly into the combustion chamber. This is accomplished by causing the inner end of the connecting rod 19 to travel in the elliptical path as shown, thus giving the pumping piston a longer stroke than the power piston. It is moving at its maximum velocity whilethe power piston is moving at its minimum velocity or is about This is very important, because of the necessity to charge the power cylinder during only a small portion of the stroke of the power piston, thereby permitting the power piston to scavengethe exhaust gases during a major portion of its outward or exhaust stroke. This makes for a very high volumetric efliciency and also increases the thermal efliciency of the engine. Furthermore, the quick action of the fuel pumping piston near the compression end of its stroke charges the power cylinder much faster than it would be charged if the pumping piston were moving at the same speed as the power piston. the charge rushes into the combustion chamber of the pow-er cylinder due to the accumulated compression pressure and the positive pumping action of the pumping piston.

After the fuel pumping piston has served the purpose of quickly charging the power In other words,

cylinder, its velocity is greatly diminished because it is reaching the outer end of its stroke about the time explosion occurs in the power cylinder. If the fuel admission valve for the power cylinder closes at the proper time, no backfiring into the pumping cylinder will be possible.

From the foregoing description, it will be seen that two-cycle engines of this type can be made to operate very elficiently even at high speeds up to more than two thousand It. P. M. The design is greatly simplified so that they can be manufactured at a reL tively low cost. The construction and arrangement is such as to enable the engine to operate as efficiently at all speeds as an ordinary fourcycle engine. lhe arrangement is very compact and the engine can be made much lighter than an ordinary four-cycle engine capable of developing the same power. Furthermore, the fuel distribution and the timing are such as to preclude the possibility of backiiring.

Obviously, the present invention is not restricted to the particular embodiment thereof herein shown and described. More over, it is not indispensable that all the features of the invention be used conjointly, since they may be employed advantageously in various combinations and sub-combinations.

What is claimed is:

1. In a two-cycle internal combustion engine having a power cylinder and piston, an associated fuel pumping cylinder and piston closely adjacent to the power cylinder; at single crank; a connecting rod for the power piston on the crank; a lateral arm on the connecting rod; a connecting rod for the pumping piston connected to said arm, the direction of rotation being such as to operate the pump piston so that it moves in advance of the power piston initially to com press a fuel charge; a head having a short fuel passage between the pump cylinder and power cylinder; and a valve for said passage arranged to open before the pump piston reaches the outer end of its stroke, whereby the final movement of the pump piston to the end of its compression stroke positively charges the working cylinder.

2. In a two-cycle internal combustion engine, a power cylinder and piston; an adj acent fuel pumping cylinder and piston; a

it c'ank and a connecting rod for the power piston; an arm on said connecting rod a connecting rod for the fuel pumping piston connected to said arm, the direction of rotation of the crank being such as to move the pumping piston at much greater velocity than and in advance of the power piston as they approach the outer ends of their respective strokes; a short fuel passage connecting the outer end of the pumping cylinder to the combustion chamber of the power cylinder; a

fuel admission valve controlling said passage and adapted to open before the pumping piston reaches the compression end of its stroke and while it is moving at its maximum velocity whereby the intially compressed fuel charge is positively and quickly forced into the combustion chamber, said valve being adapted to close when the pumping piston reaches approximately the end of its fuel charging stroke.

3. In a two-cycle internal combustion engine, a power cylinder and piston; a closely adjacent, parallel fuel pumping cylinder and piston; a crank shaft having a single crank for both pistons; a connecting rod for the power piston having a laterally projecting arm below the pumping piston; a connecting rod for the pumping piston pivotally connected to said arm, the connection being such as to give the pumping piston a longer stroke than the power piston and to impart a greater velocity to the pumping piston near the outer end portion of its stroke than the corresponding velocity of the power piston, the direction of rotation of the crank and the length of said arm being such as to move the pumping piston ahead of the power piston on its compression stroke a single head for both cylinders having a short fuel passage between the pumping cylinder and the combustion chamber of the power cylinder; a valve in said passage arranged to open before the pumping piston reaches the end of its compression stroke and to close as it reaches the end of said stroke; a valved fuel inlet passage for the pumping cylinder; and a valved exhaust passage for the power cylinder.

In testimony, that I claim the foregoing as my own, I have hereto afiixed my signature.

ELMER C. AHRENS. 

